/*
 * Copyright 2009 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.css.compiler.passes;

import com.google.common.css.compiler.ast.CssCompilerPass;
import com.google.common.css.compiler.ast.CssRulesetNode;
import com.google.common.css.compiler.ast.DefaultTreeVisitor;
import com.google.common.css.compiler.ast.MutatingVisitController;

/**
 * A compiler pass that eliminates the empty ruleset nodes.
 *
 * @author oana@google.com (Oana Florescu)
 */
public class EliminateEmptyRulesetNodes extends DefaultTreeVisitor
    implements CssCompilerPass {

  private final MutatingVisitController visitController;

  public EliminateEmptyRulesetNodes(MutatingVisitController visitController) {
    this.visitController = visitController;
  }

  @Override
  public boolean enterRuleset(CssRulesetNode node) {
    if (node.getDeclarations().isEmpty()) {
      visitController.removeCurrentNode();
      return false;
    }
    return true;
  }

  @Override
  public void runPass() {
    visitController.startVisit(this);
  }
}
